Most sea ice looks set to disappear in September within a few years. For other months, it may take a few more years for most sea ice to disappear. This is the conclusion when calculating an exponential trendline using annual sea ice volume minima,

- Why volume? It makes sense to look at volume, because the thinner the sea ice will get, the bigger the chance will be that the increasingly intense and frequent storms will smash it to pieces, leaving only a small rim of ice along the edges of Greenland and Ellesmere island.

- Why minima? Clearly, when examining the danger of disappearance of Arctic sea ice, it makes sense to compare annual moments when volume is at its minimum.

- Why an exponential trendline? A linear trend would be inappropriate, given the increased impact of feedbacks that can each be expected to reinforce sea ice decline, while there can also be interaction between these feedbacks, further accelerating sea ice decline. Albedo change is one such feedback, but there are numerous other ones, such as storms that have more chance to grow stronger as the area with open water increases. In conclusion, an exponential trendline is more appropriate than a linear trendline, as also illustrated by the image below that illustrates that a linear trendline has 9 years fall outside its 95% confidence ionterval, versus 4 years for an exponential trendline.

An exponential trendline shows that sea ice looks set to disappear in 2019, while its virtual disappearance in 2015 is within the margins of a 5% confidence interval, reflecting natural variability.

Indeed, natural variability could bring about a collapse of Arctic sea ice soon. The thinner the sea ice gets, the more likely such an early collapse is to occur. Global warming will increase the intensity of extreme weather events, resulting in stronger winds and more intense storms raging over the Arctic Ocean that can break up the thinning sea ice in small parts. Much of the sea ice loss already now occurs due to sea ice moving along the edges of Greenland into the Atlantic Ocean. As there will be ever more open water, the smaller parts can be more easily driven out of the Arctic Ocean.

2. What makes Arctic sea ice retreat so rapidly?

Emissions result in global warming, as warmer water flows into the Arctic from ocean currents and rivers. Melting permafrost causes even more emissions, while there are further feedbacks such as wildfires raging in tundras and peatlands. The Arctic is especially vulnerable to black carbon (soot), which darkens the ice, resulting in more sunlight being absorbed rather than reflected back into space. This albedo effect accelerates as sea ice retreats and amplifies warming in the Arctic.

Without action to cool the Arctic, methane releases threaten to further amplify warming, triggering runaway warming.

Permafrost and sea ice keep methane hydrates stable. Arctic sea ice and permafrost still reflect a lot of sunlight back into space, while a lot of heat also goes into the process of melting the ice. As the sea ice declines and permafrost melts, this light and heat is instead absorbed in the Arctic, further accelerating warming in the Arctic, which is already several times larger than elsewhere on Earth (see next question).

The image directly above shows the threat of feedbacks further accelerated warming in the Arctic and triggering methane releases, escalating into runaway global warming.

For more on feedbacks that are accelerating warming in the Arctic, see the feedbacks page.

4. Are temperatures already rising in the Arctic?

The image below shows observed temperature anomalies - global in blue and for higher latitudes in red, with trend added.

As above image shows, temperatures in the Arctic are rising exponentially and without action anomalies look set to reach 10 degrees Celsius within decades. Once that kind of warming starts penetrating sediments, it will be very hard to reverse the process.

5. What are the consequences of large methane releases? What is the cost of (not) taking action?

There will be many consequences, and they all look bad. One likely consequence is that high temperatures at high latitudes will cause wildfires, e.g. in Siberia, which has a very high soil carbon content (see image below).

Such fires would cause huge amounts of soot that will in part settle down on the Himalayan Plateau, darkening the ice and snow, resulting in more heat absorption there and disruption of the flow of rivers that originate there. This can make that both the supply of food and water can be severely disrupted, threatening the extinction of many species.

Glaciers on the Himalayan Plateau act as a water storage tower for South and East Asia, releasing melt water in warm months to the Indus, Ganges, Brahmaputra and other river systems, providing fresh water to more than a billion people. In the dry season glacial melt provides half or more of the water in many rivers.

As the snow melts in the spring and summer, the impact of black soot on the glacier surface increases, since the soot particles do not escape in the melt water as efficiently as the water itself. As a consequence, the soot darkens the glacier surface even more during the melt season, increasing absorption of sunlight, and speeding up glacier disintegration.

Taking no action risks extinction for many species, including humans, possibly within one generation. With so much at stake, the cost of taking action is dwarfed by the price we pay when no action is taken. The longer we wait, the larger the risk becomes and the more difficult, expensive and risky it will become to take measures to try and reduce the risk.

Methane hydrates are crystal-like structures that hold methane. They are likely to remain intact as long as they are not disturbed (e.g. by landslides or earthquakes) and temperatures and pressures remain within certain bounderies.

Pockmarks up to 11 km (6.8 mi) wide off the coast of New Zealand indicate that large abrupt emissions from methane hydrates did occur in the past.http://methane-hydrates.blogspot.com/2013/06/sea-of-okhotsk.html
Since the location of these pockmarks is prone to earthquakes, seismic activity may have contributed to the release.

Similarly, seismic activity could trigger large methane releases today. The situation is particularly dangerous in the Arctic. Warnings about this have been published for more than a decade, e.g. see the poster at the bottom of: http://arctic-news.blogspot.com/p/seismic-activity.html
In the past, hydrates did likely become destabilized as Earth became warmer during interglacial periods. But while Earth - during such periods - may have been several degrees warmer than today, warming in the Arctic probably was not as amplified as it is today. In the Eemian period, for example, there were no ice-free summers in the Arctic. Ice sheets remained largely frozen, in part because ocean currents were quite different from the situation today.

This suggest that the Arctic sea ice did not retreat enough to cause melting permafrost to destabilize many hydrates in the Eemian priod. According to Paul Beckwith of the University of Ottawa Laboratory for Paleoclimatology and Climatology, this can be explained by a number of factors:

"... the key distinction is that the warming today is from Greenhouse gases being higher and occurs 'twenty-four seven', namely the cooling at night is much less (diurnal variation smaller); in the Eemian the tilt of the Earth was much greater so there was much more seasonality, thus winters were much colder so the sea ice extent, thickness, and thus volume could build up much more, and the summers were warmer in the daytime, however the cooling at night was much greater than now (less greenhouse gas [GHG], more diurnal variation); net result is that the ice was much more durable in the Eemian. Greenland temps were higher during the daytime, but cooled off much more during the nighttime in the lower GHG concentration world."

Even where large amounts of methane did get released from hydrates, this may not have left a mark in ice cores. Paul Beckwith explains:

"The length of time for the methane pulse is very important here. If most of the methane came out in a decade, for example then within a subsequent decade or so most of the methane will have been broken down to CO2 and H20 and also been dispersed/distributed around the planet, away from the pulse source area in the Arctic. The CO2 produced would have been small (CO2 stayed within 180-280 ppm range). It takes about 50 years or even more (depending on the snowfall rate and surface melt rates) for snow at the surface to be compacted into firn that closes off the air spaces creating the bubbles in the ice that are reservoirs of the methane and other atmospheric gases. Because of that 50 year bubble closure time, the large pulse of methane that was burped out of the marine sediments and terrestrial permafrost would be long gone and not result in a detectable signal in the ice core record. Just because the record does not capture it does not mean that it was not produced."

Furthermore, methane that did get trapped in ice may have returned to the atmosphere as temperature rose and the ice melted. Higher temperatures for thousands of years ensured that the methane was over time oxidized, leaving only carbon dioxide traces in later ice, and thus in the ice cores that we examine today. For more on this point, also see the comments and responses at:

So, many large releases of methane that occurred in the past may not show up as such in records such as ice cores, but large abrupt emissions from Arctic methane hydrates did likely play a key role in the sudden massive warming 11,600 years ago at the end of the Younger Dryas cold period, according to:

There is also evidence that large methane releases to the atmosphere from deep-sea gas-hydrate dissociation occurred during the last glacial episode off the coast of Papua New Guinea, 39,000 and 55,000 years ago, as well as in the Santa Barbara Basin, which occurred in response to a warming of the intermediate waters and thus presumably of the deep-sea sediments. These deep-sea methane emissions occurred synchronously with rapid climate warmings associated with atmospheric methane increases and led Kennett et al. to propose the “clathrate gun hypothesis,” which postulates that deep-sea methane hydrates played a significant role in late quaternary climate changes.

In conclusion, there's no reason to doubt that there have been large emissions from methane hydrates in the past. Furthermore, the current situation is unprecedented and looks more dangerous in many ways than in previous periods. Firstly, the rate at which temperatures are rising, particularly in the Arctic, is without precedent. Furthermore, the levels of pollutants in the atmosphere today are extremely high (and rising), which is the more dangerous given the presence of huge amounts of methane in the shallow seas of the Arctic. For further reasons why the current situation in the Arctic is so dangerous, see point 8. below and:

8. Why is the situation in the East Siberian Arctic Shelf (ESAS) so threatening?

ESAS stands for East Siberian Arctic Shelf, an area of over 2 million square kilometers large on the edge of Siberia. ESAS is the largest continental shelf in the world, and 75% of the sea over the shelf is less than 50 meters deep.

At the last glacial maximum (LGM), at the height of the ice age about 20,000 years ago, the sea level was approximately 120 metres lower than it is today. The ESAS was well above sea level and the cold air temperature would have cooled the land surface to considerable depth, freezing water around organic matter into permafrost. Then the sea level rose, and the land and permafrost were inundated. Some of the organic matter would have decomposed, producing methane which could, at certain pressures and temperatures, combine with groundwater to form methane hydrate (a "lattice" of ice and gas). Thus, below the permafrost is now a mixture of hydrate and free methane gas.

Methane release from the East Siberian Arctic Shelf and the Potential for Abrupt Climate Change - by Natalia Shakhova and Igor Semiletov (2010)

A recent paper in Oceanology says that the ESAS is not only the broadest and shallowest shelf of the World Ocean, but also undergoes pronounced transformations under the change of climatic epochs. The shelf is also characterized by the location of over 80% of the existing submarine permafrost, as well as of the bulk of shallow water gas hydrates. The most distinctive characteristics of the Arctic compared to oceanic gas hydrates are the following:

high density of the spatial deposition; the thickness of the layer of pure gas hydrates may be as high as 100m or more, unlike the oceanic hydrates occurring mainly in disseminated form;

the presence of deposits is more likely by several times at the Arctic shelf compared to the Arctic land;

the high inter stitial saturation with gas hydrate (from 20 to 100% of the interstitial volume against 1–2% for oceanic gas hydrates);

the lower thermal capacity of the phase transition (a third of that for oceanic hydrates); and

high sensitivity to further warming, because of the profound changes in thermal conditions of the subma rine permafrost proceeding as long as 5000–6000 years.

9. How much methane could be released from the East Siberian Arctic Shelf (ESAS)?

How much methane could be released from the East Siberian Arctic Shelf (ESAS) follows from a number of factors such as how much the ESAS will warm, how much methane is stored there and how prone this methane is to be released. The question is partly answered in the response to the next question, 10., while the above image highlights an important consideration, i.e. that large abrupt releases of methane will additionally trigger further releases.

Recent geochemical and geophysical evidence demonstrates that the ESAS subsea permafrost has been showing signs of destabilization (Shakhova et al., 2010a, b). If this permafrost further destabilizes, emissions could be significantly larger than teragram-sized.

The amount of CH4 that could theoretically be released in the future is enormous. The volume of gas hydrates that underlie the Arctic Ocean seabed is estimated to be 2,000 Gt of CH4 (Makogon et al., 2007). About 85% of the Arctic Ocean sedimentary basins occur within the continental shelf; therefore, within the ESAS alone, which comprises ~30% of the area of the Arctic shelf, hydrate deposits could contain ~500 Gt of CH4. An additional two-thirds of that amount (~300 Gt) is stored in the form of free gas (Ginsburg and Soloviev, 1994). Because submarine permafrost is identical to on-land permafrost, the carbon pool held within submarine permafrost can be estimated to include not less than 500 Gt of carbon within a 25-m-thick permafrost body (Zimov et al., 2006). Thus the total amount of carbon preserved within the Arctic continental shelf could total ~1300 Gt of carbon, of which 800 Gt is previously formed CH4 ready to be suddenly released when appropriate pathways develop (Shakhova and Semiletov, 2009; Shakhova et al., 2010b). Release of only 1% of this reservoir would more than triple the atmospheric mixing ratio of CH4, probably triggering abrupt climate change, as predicted by modeling results (Archer and Buffett, 2005).A new model of subsea permafrost degradation The Arctic Ocean is surrounded by offshore and onshore permafrost, which is being degraded at increasing rates under warming conditions. This warming is most pronounced in the East Siberian part of the Arctic, where surface air temperature increased by about 5°C during 2000–2005 compared to 20th century temperature patterns (Figure 4). In response to this anomalous warming, shrinkage of onshore permafrost is projected to double by 2090 (ACIA, 2004).At the same time, no attention has been paid to that part of the onshore permafrost that is the most sensitive to warming. This sensitive permafrost was inundated during the last 10–15 Kyr, when the ocean level rose by ≤ 100 m. The thermal regime of the surrounding environment changed drastically as the sea intruded, warming by as much as 12–17°C; gradually, the temperature of the submerged permafrost responded.

11. Is it possible for heat to reach hydrates deep down in the sediment underneath the ESAS?

It is possible for heat to reach hydrates in a short period. Waters in the Arctic can be very shallow, which makes that they can heat up quite rapidly, especially in summer when the sun hardly sets in the Arctic.

As above image shows, sea surface temperature anomalies of over 5 degrees Celsius were recorded in 2007. Strong polynya activity in 2007 caused more summertime open water in the Laptev Sea, in turn causing more vertical mixing of the water column during storms in late 2007 -- bottom water temperatures on the mid-shelf increased by more than 3 degrees Celsius compared to the long-term mean.http://www.polarresearch.net/index.php/polar/article/view/6425/html_150 Drastic sea ice shrinkage causes increase in storm activities and deepening of the wind-wave-mixing layer down to depth ~50 m that enhance methane release from the water column to the atmosphere.

The ESAS is very shallow averaging < 50 m depth over its 2x10ˆ6 km2 area, 80% of which is predicted to contain originally sub-areal permafrost unit, now submerged due to transgression. Associated with transgression was a new thermal regime including enhanced heat transfer from warming Arctic Oceans and terrestrial riverine waters to the submerged permafrost, as well as from exothermic oxidation reactions and geothermal sources. As a result, large areas of integrity loss have been identiﬁed from widespread bubble ebullition and enhanced aqueous methane levels well above atmospheric equilibrium. The resulting thaw sediments (taliks) and structural breaches facilitate ﬂuid
and gas migration within the permafrost to overlying sediments where some microbial methane oxidation occurs. These destabilizing features may also provide a mechanism for enhanced heat transfer to methane hydrate deposits.http://meetingorganizer.copernicus.org/EGU2010/EGU2010-1046-2.pdf

Hydrates can exist at the end of conduits in the sediment, formed when methane did escape from such hydrates in the past. Heat can travel down such conduits relatively fast, warming up the hydrates and destabilizing them in the process, resulting in huge abrupt releases of methane.

The danger is that heat will travel down cracks, fractures, channels and conduits in the permafrost, and reach methane held in the form of free gas and hydrates in the sediment. A team of scientists studying methane emissions in the Laptev Sea point at the observed massive methane outburst from the bottom sediments in the image below as an indication that methane must be rising through channels in the sediment.

Because the waters are so shallow, much of the methane that rises up through these waters will not get oxidized. As the methane causes further warming in the atmosphere, this will causing further release of methane that further accelerates warming, in a vicious cycle leading to runaway global warming.http://arctic-news.blogspot.com/p/need-for-geo-engineering.html

12. How much methane is/was there in the atmosphere, how much is added annually?

The above figure for radiative forcing (RF of about 0.5 W per square meter) does not include indirect effects of methane, such as water vapor. These effects are included in the images below.

Source: Hansen and Sato (2001)

Source: Isaksen et al. (2011)

13. What is the global warming potential of methane?

IPCC AR5 (2013) figures for methane's lifetime and methane's Global Warming Potential (GWP) over 20 and 100 years are in the top right-hand panel below. In the panel underneath is the formula used to calculate GWP.

Note that Shindell et al. pointed out in 2009 that when including some important direct and indirect effects, methane's GWP is 105 over 20 years. Over shorter periods, the GWP is even higher, as illustrated by above image below. Over a 10-year timescale, methane's GWP is 130, as calculated by Sam Carana based on Shindell's data. Over a 10-year timescale, the current global release of methane from all anthropogenic sources exceeds all anthropogenic carbon dioxide emissions as agents of global warming; that is, methane emissions are more important than carbon dioxide emissions for driving the current rate of global warming, as illsutrated by the graph in the left-hand panel of above image. Unlike carbon dioxide, methane's GWP does rise as more of it is released.

Methane can persist in the atmosphere for as little as 8 years, but its lifetime can be extended to decades, particularly due to lack of hydroxyl in the atmosphere.

The IPCC AR5 (2013) figure for methane's lifetime is 12.4 years. Methane's GWP and lifetime depend on variables such as the size of emissions and the location of emissions (hydroxyl depletion already is a big problem in the Arctic atmosphere), the wind, the time of year (when it's winter, there's less hydroxyl), etc. Another variable is the indirect effect of large emissions and what's often overlooked is that large emissions will trigger further emissions of methane, thus further extending the lifetime of both the new and the earlier-emitted methane, which can make the methane persist locally for decades.

More monitoring should take place to analyze details of such venting. Furthermore, data should be more easily available online, while more should be done to interpret the data and assess the risks. A recent private initiative to do so has started at http://methanetracker.org

To some extent, the question how much methane is already venting in the Arctic is no longer relevant. Action can no longer be postponed. It is clear that it's necessary to reduce the risk that large amounts of methane will be released abruptly in future. We need to reduce this risk while we still can.

Methane in the Arctic is monitored through flask and in situ measurements at only three sites, i.e. Barrow (Alaska), Alert (Nunavut, Canada) and Svalbard (Norway), as discussed at: http://arctic-news.blogspot.com/p/need-for-geo-engineering.htmlMeanwhile, funding for continued in situ measuments at Barrow have been terminated.

16. What should be done to reduce the risk that methane hydrates will trigger runaway warming?

Large-scale geo-engineering, afforestation and dramatic reduction of emissions are necessary to bring the atmosphere and oceans back to their pre-industrial state as soon as possible. Additionally, further geo-engineering is necessary to reflect more sunlight back into space, break down or capture methane, etc.http://arctic-news.blogspot.com/p/need-for-geo-engineering.html

In other words, an approach is recommended that implements the following three parts in parallel:

PART A. Dramatic reductions are needed of emissions of greenhouse gases, halogens, soot and tropospheric ozone precursors such as carbon monoxide.

17. What are the costs of this proposed action (to reduce the risk of runaway warming)?

Again, as discussed under question 5.,we cannot afford not to act. Each policy that seeks to accomplish the necessary shifts comes with costs and benefits, and they will be greater for some people than for others, but generally we will all be much better off if we act. To get the atmosphere and oceans back to their pre-industrial state, feebates are the most effective policy instruments, they can be budget-neutral, have the least leakage and are best implemented locally. Such local implementation means that one doesn't have to wait for policy implementations elsewhere. While a global commitment to act is imperative, the exact shape of such policies is best decided and implemented locally. In many cases, this increases health, job and investment opportunities, while prices of products will come down over time.

Furthermore, geo-engineering methods must be deployed to reflect more sunlight back into space, break down or capture methane, etc. The direct cost of this are estimated to be under $1 billion per year. Additionally, there may be some undesirable side effects of geo-engineering, but - again - the cost of that would be dwarfed by the cost of taking no action.http://arctic-news.blogspot.com/p/need-for-geo-engineering.html

18. Shouldn't we wait with geo-engineering until more research is done?

Firstly, the question whether more research was necessary wasn't asked when emissions started, and even as the evidence of their harm accumulated, politicians refused to act. Huge amounts of sulfur have already been emitted in the past by volcanoes, coal-fired power plants and bunker fuel used by ships. Emissions associated with the burning of fuel need to be reduced, but at the same time the cooling effect of aerosols needs to be replaced, to reduce the risk of runaway global warming.

There are risks associated with any chosen policy; a business-as-usual scenario carries the highest risk of extinction of many species, including humans. With so much at stake, the cost of taking no action is incalculable. The longer we wait, the larger the risk becomes and the more difficult, expensive and risky it will become to take measures in efforts to reduce the risk.

Of course, research should continue to find the safest methods, but there's enough evidence that decisive action is necessary now, and there are many measures that can be taken that are safe and that are beneficial in many ways. There are sufficient technologies and resources available to start acting now. The one thing we don't have enough is time. We are rapidly running out of time. We cannot afford not to act.

19. Won't geo-engineering take the pressure off the need to reduce emissions?

Even with substantial geo-engineering, dramatic emissions cuts are imperative. Including geo-engineering as part of the necessary action is needed to reduce the risk that methane releases from the se4afloor of the Arctic Ocean will trigger runaway warming and to help return the atmosphere, soils and oceans to their pre-industrial state fast enough.

20. Why should drilling be banned in the Arctic? Why is a spill or blow-out particularly bad in the Arctic?

Given the risk of oil spills and disturbing methane hydrates, drilling in the Arctic should be banned. Since a rapid shift to clean energy is necessary globally, there's no need to drill for fossil fuel in the Arctic in the first place. Rather than drilling for oil and natural gas, oil companies should use their experience with drilling and with hydrates to help out in dealing with the problems.

Circumstances in the Arctic are different from most other places in the world. There is hardly any response capacity ready for launch in the Arctic, while arrival of winter ice would make it even harder to reach many places. Standard responses such as drilling relief wells or using booms are hard to apply when the ice thickens. An oil spill in the Arctic would risk that oil gets underneath the sea ice, from where it will be very hard to recover. Low temperatures mean there are less bacteria to break down the oil. In other places, currents may bring bacteria back to the location of the spill repeatedly. Currents in the Arctic are long, so once bacteria flow away from the location of the spill, it may take a long time for them to return, too long to survive in the cold water and often with little or no sunshine.

Methane won't get broken down easily in the Arctic, as this requires oxygen, which isn't quickly replenished in the Arctic, once depleted. Furthermore, hydroxyl levels in the Arctic are very low, so methane that reaches the atmosphere won't get broken down there easily either.

QUOTES:

"It seems clear that in a warming world (for whatever reason), methane will be released in increasing quantities, e.g. from warming permafrost, thus augmenting global warming. Disturbances on the sea bed may also cause the decomposition of methane-hydrate. It is known that drilling into methane hydrate poses a hazard to oil prospecting operations, and it is also thought that decomposition of methane hydrate with an eruption of methane could trigger a tsunami."

21. Why are methane concentrations in the atmosphere over the Arctic so high from October through to the northern Spring?

Huge amounts of methane are starting to get released from the Arctic Ocean's seafloor in October. Why October?

In September, when Arctic sea ice is at a minimum, huge amounts of sunlight are absorbed by the Arctic Ocean. Accordingly, a huge transfer of heat occurs from the Arctic Ocean to the atmosphere and this continues into October, when the sea ice is increasing.

As the image below shows, air temperature at 2 meters above sea level was below 0°C (32°F, i.e. the temperature at which water freezes) over most of the Arctic Ocean on October 26, 2014. The Arctic was over 6°F (3.34°C) warmer than average, and at some places was up to 20°C (36°F) warmer than average.

Above image illustrates the enormous amount of heat that is transferred from the waters of the Arctic Ocean to the atmosphere well into October, in places where sea ice has not yet covered the water. In early October, as illustrated by the image below, the Arctic Ocean starts freezes over, so less heat will from then on be able to escape to the atmosphere. Sealed off from the atmosphere by sea ice, greater mixing of heat in the water will occur down to the seafloor of the Arctic Ocean.

Furthermore, the sea ice makes that less moisture evaporates from the water, which together with the change of seasons results in lower hydroxyl levels at the higher latitudes of the Northern Hemisphere, in turn resulting in less methane being broken down in the atmosphere over the Arctic.

In October, melting of sea ice has stopped. Also, as land around the Arctic Ocean freezes over, less fresh water will flow from rivers into the Arctic Ocean. As a result, the salt content of the Arctic Ocean increases, all the way down to the seafloor of the Arctic Ocean, making it easier for ice in cracks and passages in sediments at the seafloor to melt, allowing methane contained in the sediment to escape.

Through to March the following year, salty and warm water (i.e. warmer than water that is present in the Arctic Ocean) will continue to be carried by the Gulf Stream into the Arctic Ocean, while the sea ice will keep the water sealed off from the atmosphere, so little heat and moisture will be able to be transferred to the atmosphere.

High methane levels over the Northern Hemisphere can continue throughout April, as the methane originating from the Arctic Ocean rises in the atmosphere while descending to lower latitudes and accumulating there at higher altitudes. In May, the sea ice starts to retreat more strongly and more hydroxyl starts getting produced in the atmosphere. As the year progresses, the ocean heat building up off the North American coast becomes overwhelming as it is carried along with the Gulf Stream, but it will take until October before the brunt of this heat will reach the sediments of the Arctic Ocean seafloor.

22. Why does methane show up so prominently over the Arctic at altitudes between about 4.4 and 6 km (14,400 and 19,800 ft)?

Methane eruptions from the seafloor of the Arctic Ocean occur in plumes, i.e. the rise is very concentrated inside the area of the plume, while little or no increase in methane levels is taking place outside the plume. This makes that such a plume doesn't show up well at lower altitudes on satellite images, because the plume will cover less than half the area of one pixel. The methane will show up better at higher altitudes as it spreads out over larger areas. At higher altitudes, methane will follow the tropopause (see image below), i.e. the methane will rise in altitude while moving closer to the equator.

2 comments:

The Climate Plan calls for comprehensive action through multiple lines of action implemented across the world and in parallel, through effective policies such as local feebates. The Climate Plan calls for a global commitment to act, combined with implementation that is preferably local. In other words, while the Climate Plan calls for a global commitment to take comprehensive and effective action to reduce the danger of catastrophic climate change, and while it recommends specific policies and approaches how best to achieve this, it invites local communities to decide what each works best for them, provided they do indeed make the progress necessary to reach agreed targets. This makes that the Climate Plan optimizes flexibility for local communities and optimizes local job and investment opportunities.

Thank you for the great article.I want to make a comment regarding the comparison between the linear and exponential decrease in ice volume made with PIOMAS data.In September 2015 Ice volume was around 6000 km^3 and in 2016 and 2017 Ice volume was around 5000 KM^3. Those three figures would be located outside the exponential graph confidence interval but within the linear graph confidence interval. So I suspect we probably wouldn't loose arctic ice before 2020. But who knows... things are changing rapidly.I think it is interesting to try and figure out why was ice so relatively low on the first half of 2017. As you mentioned many times, the oceans are absorbing most of the climate change. I suspect it is just a lag. Living here, close to the great lakes, seasons usually comes later. The lakes absorb the weather, and releases it about a month in delay. So Toronto's coldest month is usually February. I think that the same thing is probably happening on a Marco scale. As shown, in time, more and more super El-Ninos will come, and the ocean absorbed heat will be released to the surface. So I assume that early in the twenty twenties, we will experience a massive super El-Nino which will change the game.

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Global temperatures are rising fast. In the Arctic, temperatures are rising even faster (interactive charts below and right). For 2010 and 2011, NASA recorded anomalies of over 2°C at higher latitudes (64N to 90N), with anomalies of over 3°C at latitudes 79N and 81N in 2010.

For November 2010, anomalies of 12.5°C were recorded at latitude 71N, longitude -79 (Baffin Island, Canada). At specific moments in time and at specific locations, anomalies can be even more striking. As an example, on January 6, 2011, temperature in Coral Harbour, located at the northwest corner of Hudson Bay in the province of Nunavut, Canada, was 30°C (54°F) above average.